The advanced COMET method successfully applied by SEAFOODplus researchers

Studying how fish diets may influence the development of intestinal disorders that may lead to cancer is very difficult. A new, advanced method is being applied by SEAFOODplus researchers in the project FISHGASTRO showing how DNA damage may be influenced. The method is extremely difficult to set up and run, so the fact that it has been possible to apply it is in itself remarkable. The very first results have been obtained. Two volunteers have completed the study and had their cells subjected to the COMET analysis. It is far too early to make wide conclusions, but the successful application of the new method is encouraging.

Authors: Nina Habermann, Gerda Pot, Anouk Geelen, Ellen Kampman, Beatrice Pool-Zobel and Elizabeth K. Lund



The aim of this study is to see whether various aspects of gut health improve if we ask people to eat two extra portions of fish a week for 6 months. The importance of this intervention study has recently been highlighted following the publication of a paper from The European Investigation into Cancer and Nutrition team showing the marked reduction in risk of getting colon cancer if you eat on average more than 40g of fish a day, which are about 2 portions a week. They cannot yet say whether it matters if the fish is oil rich or not so we are dividing our volunteers into people eating white fish and those eating oil rich fish as well as a control group eating no extra fish. All our

volunteers are patients going for colonoscopy anyway and they donate us for the study 4-8 biopsies, which are tissues samples from their large bowel weighing between 4-15 mg. They then get randomised to the different intervention groups and after 6 months they return specially for us, to give a few more biopsy samples. We also take detailed diet histories, blood samples and faecal samples during the study. We have now recruited in Holland and the UK over 40 people and three have completed the study. We aim to have 270 people complete by the end of the SEAFOODplus project so we are now expanding into more hospitals and involving more doctors.


The method

We have some preliminary data using a technique called The COMET assay. It has this name because as part of the analysis method the nuclei of cells, embedded in agar, are subjected to an electrophoresis step in which any damaged DNA is pulled toward the positive electrode and when the cells are stained they look like comets. The longer the COMET tail the more DNA damage has occurred. The principle is shown in the figure.

The use of this technique on cells isolated from intestinal tissue is novel, and within the FISHGASTRO project of SEAFOODplus we have developed and perfected a technique by which this method can be partially carried out in the laboratory where the samples are first taken (Wageningen University, Holland) and then stored and sent to the collaborating laboratory (Jena University, Germany) with expertise in the analysis of these samples. This work has been performed by two PhD students working on the project, Gerda Pot in Holland and Nina Habermann in Germany.  Two volunteers have completed the study and had their cells subjected to this analysis and both seem to have less DNA damage after intervention than before but we cannot yet interpret this any further as the study must be completed before the codes are broken. It is also clear there is a very large variation in baseline values. Again the underlying cause of this will be investigated at the end of study in relation to diseases experienced by the volunteers and their diets.

Figure showing the results of the first two patients completing the studies. The others are to follow as soon as samples have been analysed.
Left: The COMET assay is performed in a room with red light
Right: Setting up electrophoresis